Levosimendan is an agent that augments myocardial contractility by increasing the sensitivity of cardiac muscle to calcium. It does this without increasing intracellular calcium concentration, which has been shown to be detrimental. Previous animal studies, and studies in healthy humans have demonstrated beneficial effects on the heart's pumping. The purpose of this study is to determine the safety and efficacy of Levosimendan vs. placebo during short term infusion in patients with chronic stable NYHA Class III-IV CHF.